Japanese Patent Publication 3-161557 discloses a weaving loom with pneumatically functioning weft thread insertion devices.
The device of the Japanese Patent Publication comprises a main weft insertion nozzle (4), a suction nozzle (12) for holding the rear end of a weft yarn or thread that has already been inserted into the weft insertion channel. The leading end of the inserted weft yarn is held by a clamp 9 at the exit side of the loom shed. In this state of the weft yarn the rear end of the weft yarn is consolidated by a gyrating twister air flow in a twister nozzle (13), for a trouble-free weaving by preventing untangling of the weft yarn forming filaments, at the rear end of the weft yarn. The suction nozzle (12) and the twister nozzle (13) are separate but aligned components. The twister air flow is effective on the rear end of the weft yarn.
When filament weft yarns of different qualities are to be woven into the same fabric in the same weaving operation, it is known to provide each weft thread with its own weft insertion components while one of the plurality of the weft threads is being actively transported through the weft insertion channel in the loom shed the other filament weft yarns are held in waiting and kept stretched by being exposed to an air stream also referred to as the so-called holding air stream having a predetermined pressure level while the other end of the stretched portion of the weft yarn is being held by a thread stopper or weft brake that cooperates with a weft yarn supply reel or spool also known as a storage spool or drum. The other weft threads or yarns that are held in waiting are exposed to the holding air stream in the respective weft yarn insertion nozzle pipe where they are exposed to a certain holding tension that is just sufficient to keep the weft thread stretched without moving the weft thread since its other end is still held by the weft stopper or weft brake.
The just described operation which applies a certain holding tension to the weft thread by the holding air stream, has the disadvantage that the filaments of the yarn can be untangled again at least partly by the holding tension, whereby particularly the weft thread ends may fan out which prevents an efficient application of the transport air streams to the weft yarn on its way through the weft insertion channel. More specifically, the required thread pulling force is not uniformly applied to the weft yarn which has a negative effect on the efficiency of the pneumatic weft insertion and on the quality of the woven fabric.
German Patent Publication DE 196 53 028 C1 discloses a method for weaving weft yarns that either are not tangled or only partially tangled, particularly synthetic filament weft yarns on weaving looms with a pneumatic weft insertion. The just mentioned known method tries to make synthetic filament yarns that conventionally have only a small internal cohesion or consolidation of the individual filaments in the yarn, suitable for weaving on air nozzle weaving looms. For this purpose the weft yarn is exposed to the operation of an entangling mechanism which is so positioned that it is effective on the weft yarn between the weft supply spool and an intermediate storage spool or drum which acts as an intermediate weft storage device to hold a predetermined weft thread length. When the known entangling mechanism is positioned between the supply spool and the intermediate storing spool it is not possible to take into account that the yarn, even though it has been entangled, will be exposed in the weft insertion nozzle pipe to an air stream that extends in the direction of weft insertion, namely the so-called holding air stream in order to temporarily keep the weft yarn in waiting or in a so-called starting position for the next following weft transport through the weft insertion channel through the loom shed. This co-called holding air stream has regularly the tendency to adversely affect the inner entangling of the filaments with one another by applying a tension force that wants to untangle the filaments at least along a certain length. If that certain length of untangled weft yarn is woven into the fabric, it is unavoidable to prevent the formation of filament loops at the catch or exit side of the loom shed. Such filaments loops, no matter how small, adversely affect the quality of the fabric.